Electric motors convert electrical energy to mechanical energy through an interaction of magnetic fields and current-carrying conductors. In contrast, generators, often referred to as dynamos, convert mechanical energy to electrical energy. Further, other electric machines, such as motor/generators and traction motors, may combine various features of both motors and generators.
Such electric machines may include an element rotatable about a central axis. The rotatable element, e.g., a rotor, may be coaxial with a static element, e.g., a stator. One type of rotor, a squirrel-cage rotor, may have a cage-like shape and include multiple longitudinal conductive rotor bars disposed between and connected to two rotor end rings. Such electric machines use relative rotation between the rotor and stator to produce mechanical energy or electric energy.